1. Field of the Invention
The present invention relates to drilling of wells in the production of oil, gas and other fluids from underground formations using a drilling fluid that reduces or prevents shale and/or clay swelling caused by the absorption of water from drilling fluids during drilling, completion and/or production.
More particularly, the present invention relates to drilling of wells in the production of oil, gas and other fluids from underground formations using a drilling fluid including a shale and/or clay treatment composition including a choline compound and an amine or quaternary ammonium clay control compound, where the composition is pre-formed or generated in situ and where the compositions stabilizes boreholes and/or reduces or prevents shale and/or clay swelling caused by the absorption of water from drilling fluids during drilling, completion and/or production.
2. Description of the Related Art
During drilling and/or completion, zones that comprise shales and/or reactive clays can become unstable, when they are in contact with water in a drilling fluid. These zones contain clays that have been dehydrated over geologic time by overburden pressure. When these zone are exposed to a water containing material such as a drilling fluid, the clays osmotically imbibe water from the drilling fluid and swell. The swelling of the shale induces stresses, loss of mechanical strength, and shale failure. See Thomas W. Beihoffer et al in the May 16, 1992 Oil & Gas Journal, page 47 et seq., entitled “Cationic Polymer Drilling Fluid Can Sometimes Replace Oil-based Mud” for a more in depth explanation of the problem of drilling through clay containing zones. Shale crumbling into the borehole (“sloughing”) can ultimately place a burden on the drill bit which makes it impossible to retrieve.
Salts such as potassium chloride have been widely used in drilling treatments to convert the formation material from the sodium form by ion exchange to, for example, the potassium form which is less vulnerable to swelling; also the use of high concentrations of potassium salts affects the osmotic balance and tends to inhibit the flow of water away from the high potassium salt concentration fluids into the shale. However, it is difficult to maintain the required high concentrations of potassium salts in the drilling fluids. In addition, the physical introduction of such salts causes difficulties with the use of the viscosifying materials typically used for drilling. Inorganic salts can also have a harmful effect on the environment if released.
There are three general types of amine and/or quaternary ammonium cation sources which have been suggested for clay treatment in during drilling operations and hydrocarbon recovery. The three types include: (a) compounds having a single-site quaternary ammonium cation and amine, (b) compounds having a few (two to about six) amine or quaternary ammonium cation sites, sometimes referred herein as “oligo-cationics”, and (c) quaternary ammonium or amine polymers, which may have from about six to thousands of cationic sites. Such prior art clay control compounds are disclosed in U.S. Pat. Nos. 2,761,835; 2,761,840; 2,761,836; 4,842,073; U.S. Pat. Nos. 5,211,239; 2,761,843; 3,349,032; 4,447,342; 4,374,739; 4,366,071 and 6,921,742, incorporated herein by reference.
Although there are numerous examples of drilling fluids having clay control additives, there is still a need in the art for drilling fluids having new clay control additives.